No description available.

No description available.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 120-129).

The purpose of this work is to develop a reliable procedure for determination of liquid phase heats of adsorption via a flow calorimetric technique. The second objective is to study heats of adsorption of target sulfur compounds on potential desulfurization sorbents. Thirdly, we strive to relate the data obtained to the properties of both the sorbent and sorbates studied. Finally, the ultimate goal of this research is to use the data obtained to develop a high capacity selective adsorbent for the desulfurization of diesel fuel. Liquid phase flow adsorption experiments were conducted on sodium-Y zeolite (NaY), nickel exchanged NaY zeolite (NiY) and cesium-exchanged NaY zeolite (CsY). The solutions used in calorimetric experiments included naphthalene in n-hexadecane (C16), dibenzothiophene (DBT) in C16, and quinoline in C16. These solutions were used to model the adsorption of aromatic, sulphur-containing and nitrogen-containing compounds in diesel fuel, respectively. Additional experiments were conducted using equimolar concentrations of all three species in C16 to examine competitive adsorption behaviour of the mixture. During heat flow experiments, effluent samples were collected and analysed to obtain breakthrough curves for the systems. Heat of adsorption data were obtained via flow microcalorimetry using a novel procedure developed by this group. In this study, some experiments were conducted to examine the repeatability and utility of this new method. Characterization experiments were also conducted including BET surface area analysis, X-Ray diffraction (XRD) analysis and Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES) analysis to determine the properties of the sorbents. These properties were then related to data obtained in flow adsorption calorimeter experiments. A detailed discussion on the development of a novel method for determination of liquid phase heats of adsorption is presented. Analysis of calculation results using this new method show good repeatability relative to the previous method used. Equilibrium adsorption relationships are developed using the Langmuir adsorption model, and these results are compared to flow adsorption results obtained from the calorimeter. Results indicate that in terms of desulfurization capability, NaY appeared to be the best sorbent. Heats of adsorption were only moderate on NaY, indicating that regeneration of the sorbent would not be difficult, and NaY had the highest sulfur capacity of the sorbents studied. This result was not in agreement with literature results, and it is proposed that the discrepancy is the result of disruption of the crystalline structure of our sorbents during the modification process. Recommendations are presented for ongoing work, including important calorimeter experiments, modifications for improvement of experimental procedure and apparatus, additional sorbent characterization for elucidation of adsorption mechanisms, and finally experiments for verification and further validation of our innovative experimental technique.

The purpose of this work is to develop a reliable procedure for determination of liquid phase heats of adsorption via a flow calorimetric technique. The second objective is to study heats of adsorption of target sulfur compounds on potential desulfurization sorbents. Thirdly, we strive to relate the data obtained to the properties of both the sorbent and sorbates studied. Finally, the ultimate goal of this research is to use the data obtained to develop a high capacity selective adsorbent for the desulfurization of diesel fuel. Liquid phase flow adsorption experiments were conducted on sodium-Y zeolite (NaY), nickel exchanged NaY zeolite (NiY) and cesium-exchanged NaY zeolite (CsY). The solutions used in calorimetric experiments included naphthalene in n-hexadecane (C16), dibenzothiophene (DBT) in C16, and quinoline in C16. These solutions were used to model the adsorption of aromatic, sulphur-containing and nitrogen-containing compounds in diesel fuel, respectively. Additional experiments were conducted using equimolar concentrations of all three species in C16 to examine competitive adsorption behaviour of the mixture. During heat flow experiments, effluent samples were collected and analysed to obtain breakthrough curves for the systems. Heat of adsorption data were obtained via flow microcalorimetry using a novel procedure developed by this group. In this study, some experiments were conducted to examine the repeatability and utility of this new method. Characterization experiments were also conducted including BET surface area analysis, X-Ray diffraction (XRD) analysis and Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES) analysis to determine the properties of the sorbents. These properties were then related to data obtained in flow adsorption calorimeter experiments. A detailed discussion on the development of a novel method for determination of liquid phase heats of adsorption is presented. Analysis of calculation results using this new method show good repeatability relative to the previous method used. Equilibrium adsorption relationships are developed using the Langmuir adsorption model, and these results are compared to flow adsorption results obtained from the calorimeter. Results indicate that in terms of desulfurization capability, NaY appeared to be the best sorbent. Heats of adsorption were only moderate on NaY, indicating that regeneration of the sorbent would not be difficult, and NaY had the highest sulfur capacity of the sorbents studied. This result was not in agreement with literature results, and it is proposed that the discrepancy is the result of disruption of the crystalline structure of our sorbents during the modification process. Recommendations are presented for ongoing work, including important calorimeter experiments, modifications for improvement of experimental procedure and apparatus, additional sorbent characterization for elucidation of adsorption mechanisms, and finally experiments for verification and further validation of our innovative experimental technique.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 159-165).

Electrochemical and thermochemical studies have been conducted to determine the thermodynamic functions, i.e., the standard free energy (ΔG°); entropy (ΔS°), and enthalpy (ΔH°) changes, for the adsorption of xanthates on pyrite. The electrochemical technique is based on the measurement of the open-circuit potentials of a pyrite electrode immersed in xanthate solutions at various temperatures. The thermochemical technique involves the determination of the heats of adsorption of xanthates on pyrite using a microcalorimeter. The electrochemical studies have shown that the ΔG° of the proposed half-cell reaction, i.e., 2X^- X₂ + 2e, is negative for all the xanthate homologues, i.e., potassium ethyl xanthate (KEX), potassium amyl xanthate (KAX), and potassium octyl xanthate (KOX), investigated. The major contribution to the free energy of adsorption comes from the -TΔS° term, while ΔH° is working adversely toward the negative free energy change. It has also been found that ΔG° increases with increasing hydrocarbon chain length and temperature. The calorimetric heats of adsorption of xanthate on pyrite increase significantly with decreasing surface coverage below the monolayer point, suggesting that xanthate adsorption on pyrite involves a heterogeneous surface reaction. Above the monolayer point, the calorimetric heats of adsorption remain constant, the magnitudes increasing in the order of KEX < KAX < KOX. The calorimetric heats of adsorption in the multilayer region are comparable to the standard enthalpy of adsorption determined from the electrochemical data by considering the cathodic reaction involving oxygen reduction. / M.S.

In this work the magnesium, zinc, nickel and cobalt MOFs of the MOF-74 isostructural family are used to probe metal-dependent adsorbate interactions with water and with carbon monoxide because of their ability to generate open metal sites upon activation. An isostructural family is used so that the only variable from one MOF to another is the metal incorporated into the framework. For water adsorption isotherms with humidities up to 90%, the observed trend at 298K and 1 bar is Mg-MOF-74 > Zn-MOF-74 > Co-MOF-74 > Ni-MOF-74. This observed trend is due to Lewis acid-base interactions. When the weight effect is removed, differences are still observed, especially below 40% relative humidity, thereby confirming that there is a metal effect. These studies revealed that PXRD alone cannot indicate the level of structural decomposition and that none of the four isostructures fully retain their structural integrity on exposure to humidified air because of microstrain and/or the presence of oxygen; more studies examining the extent of structural decomposition need to be undertaken. For carbon monoxide adsorption the general observed trend for P < 4 bar and temperatures of 298, 313 and 333K is Co-MOF-74 > Ni-MOF-74 > Zn-MOF-74 > Mg-MOF-74. This trend is based on π-backbonding interactions. Here again, differences remain after removal of the weight effect, confirming the metal dependence. Notably, Co-MOF-74 has the highest CO loading at 298K and 1 bar reported so far. Both the Toth and Virial Isotherms were used to fit the CO adsorption data followed by the use of the Clausius-Clapeyron equation to find the isosteric heats of adsorption, qst. The results from the Toth isotherm are more reliable and showed that qst remains constant as loading increases for Mg-MOF-74, decreases for Zn-MOF-74 and increases with loading for Co-MOF-74 and Ni-MOF-74; Ni-MOF-74 had the highest heat of adsorption at all loadings. It appears that using the Clausius-Clapeyron equation to calculate qst is an inappropriate method for Ni-MOF-74 so other methods such as calorimetry are recommended. It is also recommended to model the data of all the MOFs with other isotherm models such as Sips equation and to investigate the possibility of chemisorption for the cobalt and nickel isostructures. Finally, Henry’s constant results reveal that Ni-MOF-74 has the highest affinity for CO at low coverages.

No description available.

Multiwalled carbon nanotubes (MWNTs) have attracted great interest during thelast decade due to their possession of a unique set of properties. In addition totheir strength, MWNTs have well defined morphologies, with large aspect ratiosand pores in the meso range, and intriguing transport properties, such as highelectrical and thermal conductivity.We are interested in how variations in the MWNT morphology affect areas ofpossible engineering applications. We have identified morphology as a criticalelement for the performance of MWNTs in engineering applications. Specificareas studied and reported here spans from surface adsorption and capillarycondensation, to dispersion and dispersion processes, and transport propertiesin relation to MWNT aspect ratio. This wide range of exploration is typicallyneeded for evaluating opportunities for new materials.MWNTs can be used in different types of adsorption systems and it should bepossible to tailor the MWNT morphology to suit a specific adsorption process.We found that the major part of butane, our model gas, adsorbs on the externalMWNT and only a small fraction ends up in the pores.The unusually large aspect ratio makes MWNTs ideal as fillers in polymermatrixes. Since MWNTs are electrically conductive, it is possible to align theMWNTs in the matrix before curing. We investigated the effect of AC-fields onaqueous MWNT dispersions and the possibility to align MWNTs in an electricalfield.It is also necessary to develop suitable dispersion methods, to enable theproduction of homogeneous dispersions and composites. We studied a numberof different mechanical dispersion methods and their effect on the MWNTmorphology.